Back-pressure control in a telecommunications network

ABSTRACT

Back-pressure control in a telecommunications network, in which a method of back-pressure control in a transport network is provided. A buffer state of a buffer is monitored. A condition indicative of back-pressure is also determined in response to a change of the buffer state passing a predetermined limit. In response to determining the condition indicative of back-pressure, a back-pressure notification message is created and, subsequently, transmitted to at least one second network node.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 16/079,540,filed Aug. 23, 2018, which is a National stage of InternationalApplication No. PCT/SE2016/050145, filed Feb. 25, 2016, which are allhereby incorporated by reference. This international patent applicationis related to the international patent application no.PCT/SE2016/050144, filed on Feb. 25, 2016 and entitled “CONGESTIONCONTROL IN A TELECOMMUNICATIONS NETWORK”.

In order to give context to this disclosure, the disclosure of theabove-referenced patent application is therefore expressly incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The present disclosure generally relates to telecommunications and, moreparticularly, to control of back-pressure in a telecommunicationsnetwork. More specifically, the present disclosure relates to systems,methods, nodes, and computer program for back-pressure control in atransport network. Embodiments described herein may advantageouslyapplied after congestion has been detected and is compensated for in thetelecommunications network.

BACKGROUND ART

It is a well-known fact that telecommunication networks utilizingresources shared between the users may experience congestion. Congestionmay, for example, occur when the sum of traffic of an ingress node ofthe shared resource exceeds the sum of the traffic of an egress node ofthe same shared resource. A typical example is a router with a specificnumber of connections. Even if the router has processing power enough tore-route the traffic according to an estimated link throughput, acurrent link throughput might in fact restrict the amount of trafficthat the outgoing links from the router can cope with. Hence, as aresult, the buffer(s) of the router may build up and eventuallyoverflow. The network then experiences congestion and the router mayalso be forced to drop data packets.

The normal behavior for any routing node is to provide a buffer(s) thatcan manage a certain amount of variation in input/output link capacityand hence absorb minor congestion occurrences. However, when thecongestion is severe, the routing node will eventually begin to dropdata packets.

Transmission Control Protocol (TCP) is a connection-oriented,congestion-controlled and reliable transport protocol. For TCP traffic,a dropped data packet will typically be detected by the sender since noacknowledgment (ACK) is received for that particular data packet and are-transmission of the data packet will occur. Further, the TCP protocolhas a built in rate adaptive mechanism which will lower the transmissionbit-rate when data packet losses occur and re-transmissions occur on theInternet Protocol (IP) layer. Hence, TCP is generally speaking wellsuited to respond to network congestion.

SUMMARY OF THE INVENTION

It is in view the above considerations and others that the embodimentsof the international patent application PCT/SE2016/050144 have beenmade.

PCT/SE2016/050144 recognizes the fact some existing solutions forcongestion control may be inadequate, especially in the next generations(e.g., 5G or beyond) of telecommunication networks. Hence, thedisclosure of PCT/SE2016/050144 proposes embodiments that allow forimproved congestion control.

The embodiments described in PCT/SE2016/050144 may advantageously beapplied in a in a fifth or future generation telecommunications network.

PCT/SE2016/050144 therefore recognizes the fact that current studies ofthe fifth generation of telecommunication networks (also known as 5G)describe a midhaul as part of the Radio Access Network (RAN)architecture. Embodiments described throughout PCT/SE2016/050144 relateto, but are not necessarily limited to, congestion control in thismidhaul. The mix of different link speeds in the network may introducerate mismatch. Furthermore, congestion may be caused by the aggregationof traffic from many sources. Additionally, or alternatively, congestionmay be caused due to differences in speed between the various networklinks. For example, congestion may occur when the demand for networkresources exceeds the available resources at some point of time in thenetwork. As will be appreciated, too much traffic may create bufferoverflow and data packet loss in the various network nodes and in themidhaul.

PCT/SE2016/050144 recognizes that existing solutions have tried to copewith similar problems in earlier generations of telecommunicationnetworks (e.g., 2G, 3G and 4G). However, PCT/SE2016/050144 additionallyrecognizes that the existing solutions may in fact be inadequate for thenext generations of telecommunication networks, such as 5G or beyond.For example, in the protocol layers, congestion control (also sometimesreferred to as flow control herein) could be solved at respectiveprotocol layers, such as TCP (i.e., at Layer 4). Local Area Networkswitches could operate at link layer and provide pause signalingmechanisms to complement end-to-end flow control. However, for the newproposed 5G architecture, none of these functions would work in anoptimal manner and would typically not work at the Internet Protocol(IP) Layer (i.e., Layer 3). Hence, new congestion control mechanisms aredesired.

In order to give context to the embodiments described inPCT/SE2016/050144 as well as the embodiments described throughout thisdisclosure, reference is now made to FIG. 1 which schematically shows anexample of a midhaul architecture for a 5G RAN architecture. As can beseen from FIG. 1, the midhaul architecture may comprise severaldifferent network nodes, such as Base Band Units (BBU), Routers, andPacket Processing Units (PPU). In the 5G RAN architecture, BBUs and PPUsmay be operatively connected over the midhaul using high speed links.The transport efficiency should advantageously be high and latency istypically required to be low. As a consequence, efficient flow controland overload protection is generally important in the transport part(a.k.a. the midhaul part) of the network, i.e. in the transport network,in order to keep the transport latency and buffer usage at low, oracceptable, levels. In the distributed 5G RAN architecture, thecongestion domain is typically between BBUs and PPUs.

As can be seen in FIG. 1, the 5G RAN architecture may also comprise aRadio Control Unit (RCU). The RCU may have a S1-AP interface. S1-AP isan abbreviation for S1 Application Protocol. S1-AP provides thesignaling service between E-UTRAN and the evolved packet core (EPC). Ascan also be seen in FIG. 1, the PPU may have a S1-u interface. S1-AP andS1-u per se are known among practitioners in the art and will thereforenot be further detailed herein.

In the 5G RAN architecture, the midhaul transport resources are notunlimited and this may result in overload of the midhaul at differentpoints (e.g., network nodes such as BBUs and/or PPUs and/or Routers) inthe transport network. In other words, there are many potentialbottlenecks where congestion may occur.

For example, the congestion may occur between BBUs and PPUs. Onepotential challenge might become the many acknowledgement (ACK) andnon-acknowledgement (NACK) messages that are communicated over themidhaul between the BBUs and PPUs. The present disclosure recognizes thefact that, in today's Long Term Evolution (LTE) evolved NodeB (eNB)deployment, the Radio Link Control (RLC) and Packet Data ConvergenceProtocol (PDCP) are co-located and any ACK and/or NACK signaling betweenthe protocol layers is very fast. However, the split of the RLC into theBBU and the PDCP into the PPU in the 5G RAN architecture will mostlikely introduce latency. At the same time the new transport network(i.e., the midhaul) between the BBU and PPU may introduce uncontrolledcharacteristics, like latency capacity and packet dropping.

It is in view of the above considerations and others that the variousembodiments disclosed in PCT/SE2016/050144 have been made. To addressthis, PCT/SE2016/050144 inter alia proposes a system for congestioncontrol in the transport network. The system comprises a first networknode (a.k.a. detection point) and at least one second network node(a.k.a. reaction point). The first network node monitors a buffer stateof a buffer, e.g. a buffer which is integral with the first networknode. Advantageously, the buffer is dynamically sampled such that thesampling rate is adjusted in dependence of the buffer state.Furthermore, the first network node determines, or otherwise detects, acondition indicative of congestion in response to a change of the bufferstate exceeding a predetermined limit. In response to determining thecondition indicative of congestion, the first network node creates acongestion notification message including a combination of: (1) a flowidentifier and (2) back-off information. Still further, the firstnetwork node transmits the congestion notification message to at leastone second network node. The at least one second network node receivesthis congestion notification message. Accordingly, the at least onesecond network node may, as a result, adjust one or more parameters onthe basis of said back-off information.

The provision of buffer state monitoring, e.g., by dynamically samplingthe buffer state makes it possible to improve the congestion control.The first network node creates a congestion notification message inresponse to determining the condition indicative of congestion. Thiscongestion notification message is transmitted to one or several secondnetwork nodes. Based on the received congestion notification message,the one or several second network nodes may compensate for a detectedcongestion by adjusting one or more of their parameters based onreceived back-off information including e.g. suggested back-off time,back-off rate, ramp-up time. Upon adjusting one or more of itsparameters, it is possible for a second network node to adaptivelyadjust its behavior in dependence of a condition indicative ofcongestion detected by any first network node in the network. This wayit is, for example, possible to dynamically reduce PDCP transmissionsand/or retransmissions that would otherwise occur more frequentlythroughout the network. As a result, the transport network will operatemore efficiently. As a further consequence, the user experience willthus also be improved.

It is in view of the above considerations and others that the variousembodiments described throughout this disclosure have been made. Thepresent disclosure recognizes the fact that there may exist scenarios,or situations, were the transport network (i.e., the midhaul) may stillnot be utilized in an optimal manner, or may not be utilizedsufficiently efficiently.

Accordingly, it is a general object of the embodiments of the presentinvention to allow for improved transport network efficiency. It wouldbe particularly advantageous if the embodiments are suitable for a fifthor future generation telecommunications network. Furthermore, it wouldbe advantageous if the solution is backwards compatible with earliergeneration telecommunications networks, such as Long Term Evolution(LTE) or LTE Advanced.

In a first aspect, this disclosure concerns a method of back-pressurecontrol in a transport network (a.k.a. midhaul). The method is performedby a first network node. The first network node may advantageously, butnot necessarily, be a network node configured for a fifth or subsequentgeneration telecommunications network. Sometimes, the first network nodemay be referred to as a detection point throughout this disclosure.Sometimes a detection point may alternatively be referred to as anoverload point.

A buffer state of a buffer is monitored. In some embodiments, the bufferstate may be monitored by dynamically sampling the buffer such that thesampling rate is adjusted in dependence of the buffer state. Forexample, the buffer may be a buffer which is part of the first networknode. As will be appreciated, it is not necessary that the buffer is abuffer that is part of the first network node. The buffer mayalternatively be external to the first network node. Nevertheless, inadvantageous embodiments the buffer is integral with the first networknode.

Furthermore, a condition indicative of back-pressure is determined inresponse to a change of the buffer state passing a second predeterminedlimit. In response to determining the condition indicative ofback-pressure, a back-pressure notification message is created, orotherwise generated. The back-pressure notification message includes acombination of (1) a flow identifier identifying a flow that contributesto back-pressure and (2) back-pressure compensation informationindicating a suitable compensation (e.g., reduction) for theback-pressure caused by the flow associated with said flow identifier.

The back-pressure compensation information may, for example, include oneor more of the following parameters: back-off rate, back-off time,ramp-up time.

In some embodiments, the flow identifier may include a Packet DataConversion Protocol (PDCP) Flow Identification (FID). Alternatively, theflow identifier may include a PDCP Group FID. Alternatively, the flowidentifier may include a PDCP Multicast Group FID. Additionally, theflow identifier may also comprise an Internet Protocol (IP) addressassociated with the first network node.

Still further, the back-pressure notification message is transmitted,i.e. sent, to a second network node.

In some embodiments, the buffer state may be a buffer fill level and thechange of the buffer state may be a change of the buffer fill level. Themethod may comprise monitoring the buffer fill level and determining thecondition indicative of back-pressure in response to the buffer filllevel descending below the second predetermined limit.

In some embodiments, the buffer state may be a buffer emptying rate atwhich the buffer empties and the change of the buffer state may be achange of the buffer emptying rate. The method may comprise monitoringthe buffer emptying rate at which the buffer state empties anddetermining the condition indicative of back-pressure in response tosaid buffer emptying rate exceeding the second predetermined limit.

In advantageous embodiments, the method may additionally comprise one ormore of the following actions, or steps, prior to determining thecondition indicative of back-pressure: determining a conditionindicative of congestion in response to a change of the buffer stateexceeding a first predetermined limit; in response to determining thecondition indicative of congestion, creating a congestion notificationmessage including a combination of: said flow identifier identifying aflow that contributes to congestion; and back-off indicating a suitableback-off to compensate for the congestion caused by the flow associatedwith said flow identifier; and transmitting the congestion notificationmessage to the second network node.

In some embodiments, the action or step of transmitting theback-pressure notification message to the second network node isperformed only in response to a congestion notification message havingbeen previously transmitted to the same second network node.

For example, the method may also comprise: storing a list of secondnetwork nodes to which the congestion notification message has beentransmitted; storing the flow identifiers and the back-off informationof all transmitted congestion notification messages; checking the storedlist of second network nodes as well as the stored flow identifiers andthe back-off information of all transmitted congestion notificationmessages to identify a second network node that is currentlycompensating for congestion; and in response to identifying at least onesecond node that is currently compensating for congestion, transmittingthe back-pressure notification message to each one of the at least onesecond network node that has been identified to be currentlycompensating for congestion.

In a second aspect, this disclosure concerns a method of back-pressurecontrol in a transport network (a.k.a. midhaul). The method is performedby a second network node. The second network node may advantageously,but not necessarily, be a network node configured for a fifth orsubsequent generation telecommunications network. Sometimes, the secondnetwork node may be referred to as a reaction point throughout thisdisclosure. Sometimes a reaction point may alternatively be referred toas a balance point.

A back-pressure notification message is received from the first networknode. The back-pressure notification message includes a combination of(1) a flow identifier identifying a flow that contributes toback-pressure and (2) back-pressure compensation information indicatinga suitable compensation (e.g., reduction) for the back-pressure causedby the flow associated with said flow identifier. Furthermore, one ormore parameters are adjusted or otherwise changed on the basis of saidback-pressure compensation information.

In a third aspect, this disclosure concerns a computer program,comprising instructions which, when executed on at least one processor,cause the at least one processor to carry out the method according toany one of the first and second aspects described hereinabove.

Furthermore, a carrier comprising the computer program may also beprovided. The carrier may, e.g., be one of an electronic signal, anoptical signal, a radio signal, or a computer readable storage medium.

In a fourth aspect, a first network node for back-pressure control in atransport network is provided. The first network node is configured toperform the method according to the earlier-described first aspect.

The first network node comprises means adapted to monitor a buffer stateof a buffer; means adapted to determine a condition indicative ofback-pressure in response to a change of the buffer state passing asecond predetermined limit; means adapted to create a back-pressurenotification message in response to determining the condition indicativeof back-pressure, the back-pressure notification message including acombination of (1) a flow identifier identifying a flow that contributesto back-pressure and (2) back-pressure compensation informationindicating a suitable compensation (e.g., reduction) for theback-pressure; and means adapted to transmit the back-pressurenotification message to a second network node.

The back-pressure compensation information may, for example, include oneor more of the following parameters: back-off rate, back-off time,ramp-up time.

In some embodiments, the flow identifier may include a Packet DataConversion Protocol (PDCP) Flow Identification (FID). Alternatively, theflow identifier may include a PDCP Group FID. Alternatively, the flowidentifier may include a PDCP Multicast Group FID. Additionally, theflow identifier may also comprise an Internet Protocol (IP) addressassociated with the first network node.

In some embodiments, the first network node of claim may also comprisemeans adapted to dynamically sample the buffer such that the samplingrate is adjusted in dependence of the buffer state.

In some embodiments, the buffer state may be a buffer fill level and thechange of the buffer state may be a change of the buffer fill level. Thefirst network node may comprise means adapted to monitor the buffer filllevel and means adapted to determine the condition indicative ofback-pressure in response to the buffer fill level descending below thesecond predetermined limit.

In some embodiments, wherein the buffer state may be a buffer emptyingrate at which the buffer empties and the change of the buffer state maybe a change of the buffer emptying rate. The first network node maycomprise means adapted to monitor the buffer emptying rate at which thebuffer state empties and means adapted to determine the conditionindicative of back-pressure in response to said buffer emptying rateexceeding the second predetermined limit.

In some embodiments, the first network node may additionally comprisemeans adapted to determine a condition indicative of congestion inresponse to a change of the buffer state exceeding a first predeterminedlimit; means adapted to create a congestion notification message inresponse to determining the condition indicative of congestion, thecongestion notification message including a combination of: (1) a flowidentifier identifying a flow that contributes to congestion; and (2)back-off information indicating a suitable back-off to compensate forthe congestion caused by the flow associated with said flow identifier;and means adapted to transmit the congestion notification message to thesecond network node.

In some embodiments, the means adapted to transmit the back-pressurenotification message to the second network node is further adapted totransmit the back-pressure notification message to the second networknode only in response to that a congestion notification message havingbeen previously transmitted to the same second network node.

In some embodiments, the first network node may further comprise meansadapted to store a list of second network nodes to which the congestionnotification message has been transmitted; means adapted to store theflow identifiers and the back-off information of all transmittedcongestion notification messages; means adapted to check the stored listof second network nodes as well as the stored flow identifiers and theback-off information of all transmitted congestion notification messagesto identify a second network node that is currently compensating forcongestion; and means adapted to transmit the back-pressure notificationmessage to each one of the at least one second network node that hasbeen identified to be currently compensating for congestion, in responseto identifying at least one second node that is currently compensatingfor congestion.

In a fifth aspect, a second network node for back-pressure control in atransport network is provided. The second network node is configured toperform the method according to the earlier-described second aspect.

The second network node comprises means adapted to receive aback-pressure notification message from the first network node. Theback-pressure notification message includes a combination of (1) a flowidentifier identifying a flow that contributes to back-pressure and (2)back-pressure compensation information indicating a suitablecompensation (e.g., reduction) for the back-pressure caused by the flowassociated with said flow identifier; and means adapted to adjust one ormore parameters on the basis of said back-pressure compensationinformation.

The various embodiments described herein allow for a novel mechanism forback-pressure control which may be particularly suitable and/or usefulfor a 5G RAN architecture.

The various embodiments described herein suggest monitoring a bufferstate of a buffer, e.g., by dynamically sampling the buffer such thatthe sampling rate is adjusted in dependence of the buffer state. Upon adetermination by a first network node (a.k.a. detection point) of acondition indicative of back-pressure in response to a change of thebuffer state passing a second predetermined limit, a back-pressurenotification message can be created or otherwise generated. Thisback-pressure notification message can be transmitted from the firstnetwork node to one or several second network nodes (a.k.a. reactionpoints). Based on the received back-pressure notification message, theone or several second network nodes may compensate for a detectedback-pressure by adjusting one or more of its parameters based onreceived information back-pressure compensation information includinge.g. suggested back-off time, suggested back-off rate, and/or suggestedramp-up time. Hence, a second network node may adjust i) the time duringwhich it performs back-off, ii) the rate at which back-off is performed,and/or iii) the ramp-up time for the back-off. Upon adjusting one ormore of its parameters, it is possible for the second network node toadaptively adjust its behavior in dependence of a condition indicativeof back-pressure detected by any first network node in the network, e.g.following an earlier detection of a condition indicative of congestionmade by the same first network node. This way it is possible toadaptively influence the PDCP transmissions/retransmissions in thenetwork at appropriate times. As a result, the transport network mayoperate more efficiently. Also, the user experience may thus beimproved.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages will be apparent andelucidated from the following description of various embodiments,reference being made to the accompanying drawings, in which:

FIG. 1 illustrates an example of a midhaul architecture;

FIGS. 2A-2G are flowcharts of a method according to an embodiment;

FIGS. 3A-3D illustrate example embodiments of a congestion notificationmessage;

FIGS. 4A-4D illustrate example embodiments of a back-pressurenotification message;

FIGS. 5A-5B illustrate examples in an IPv6 and a IPv4 environments,respectively,

FIG. 6 is a flowchart of a method according to an embodiment;

FIG. 7 illustrates an example embodiment of a first network node;

FIG. 8 illustrates an example implementation of the first network nodein FIG. 7;

FIG. 9 illustrates an example implementation of the first network nodein FIG. 7;

FIG. 10 illustrates an example embodiment of a second network node;

FIG. 11 illustrates an example implementation of the second network nodein FIG. 10;

FIG. 12 illustrates an example implementation of the second network nodein FIG. 10; and

FIG. 13 illustrates a carrier comprising a computer program, inaccordance with an embodiment.

DETAILED DESCRIPTION

The invention will now be described more fully hereinafter. Theinvention may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments set forth herein; rather,these embodiments are provided by way of example so that this disclosurewill be thorough and complete, and will fully convey the scope of thetechnology to those persons skilled in the art. Like reference numbersrefer to like elements throughout the description.

As described above, some existing solutions for congestion control maybe inadequate, especially in the next generations (e.g., 5G or beyond)of telecommunication networks. This disclosure recognizes that there isa need for a solution that allows for improved network efficiency.

Accordingly, it is a general object of the embodiments of the presentinvention to allow for improved network efficiency.

To address this, in accordance with an embodiment, described herein is asystem for back-pressure control in a transport network. The systemcomprises a first network node (a.k.a. detection point) and at least onesecond network node (a.k.a. reaction point). The first network nodemonitors a buffer state of a buffer, e.g. a buffer which is integralwith the first network node. Advantageously, the buffer is dynamicallysampled such that the sampling rate is adjusted in dependence of thebuffer level. Furthermore, the first network node determines orotherwise detects a condition indicative of back-pressure in response toa change of the buffer state passing a second predetermined limit. Inresponse to determining the condition indicative of back-pressure, thefirst network node creates a back-pressure notification messageincluding a combination of a flow identifier identifying a flow thatcontributes to back-pressure and back-pressure compensation informationindicating a suitable compensation (e.g., reduction) for theback-pressure caused by the flow associated with said flow identifier.Still further, the first network node transmits the back-pressurenotification message to at least one second network node. The at leastone second network node receives this back-pressure notificationmessage. Accordingly, the at least one second network node may, as aresult, adjust one or more parameters on the basis of said back-pressurecompensation information.

Hence, it is suggested to monitor a buffer state of a buffer, e.g., bydynamically sampling the buffer such that the sampling rate is adjustedin dependence of the buffer state. Upon a determination by the firstnetwork node of a condition indicative of back-pressure in response to achange of the buffer state passing a second predetermined limit, theback-pressure notification message can be created or otherwisegenerated. This back-pressure notification message can be transmittedfrom the first network node to one or several second network nodes.Based on the received back-pressure notification message, the one orseveral second network nodes may compensate for a detected back-pressureby adjusting one or more of its parameters based on received informationback-pressure compensation information including e.g. suggested back-offtime, suggested back-off rate, and/or suggested ramp-up time. Hence, asecond network node may adjust i) the time during which it performsback-off, ii) the rate at which back-off is performed, and/or iii) theramp-up time for the back-off. Upon adjusting one or more of itsparameters, it is possible for the second network node to adaptivelyadjust its behavior in dependence of a condition indicative ofback-pressure detected by any first network node in the network, e.g.following an earlier detection of a condition indicative of congestionmade by the same first network node. This way it is possible toadaptively influence the PDCP transmissions/retransmissions in thenetwork at appropriate times. As a result, the transport network mayoperate more efficiently.

With reference to FIGS. 2 A-G, a method according to an exampleembodiment will be described in further detail. FIG. 2A-D illustrateactions, or steps, of an example method of congestion control in atransport network. FIGS. 2E-G illustrate actions, or steps, of anexample method of back-pressure control in the transport network. Themethod described in conjunction with FIGS. 2A-2E is performed by a firstnetwork node (a.k.a detection point). This first network node isadvantageously a network node that is configured for a fifth orsubsequent generation telecommunication network.

As can be seen in FIG. 2A, a buffer state of a buffer may be monitored210. For example, the buffer may be a buffer which is part of the firstnetwork node. In some embodiments, the buffer is thus integral with thefirst network node. As will be appreciated, it is not necessary that thebuffer is part of the first network node. In alternative embodiments,the buffer may be external to the first network node.

In advantageous embodiments, the monitoring 210 may optionally comprisedynamically sampling the buffer such that the sampling rate is adjustedin dependence of the buffer state.

Furthermore, a condition indicative of congestion may be determined 220in response to the buffer state exceeding a first predetermined limit.The exact level, or value, of this predetermined limit should be testedand evaluated in each specific case, e.g. in view of system requirementsand/or user demands.

In one embodiment, which is schematically illustrated in FIG. 2C, theearlier-mentioned buffer state may be a buffer fill level. Hence, thebuffer fill level may be monitored 211. Also, the condition indicativeof congestion may be determined 221 in response to the buffer fill levelexceeding the first predetermined first limit.

In an alternative embodiment, which is schematically illustrated in FIG.2D, the earlier-mentioned buffer state may be a buffer change rate atwhich the buffer changes. Hence, the rate at which the buffer changesmay be monitored 212. Also, the condition indicative of congestion maybe determined 222 in response to said buffer change rate exceeding thefirst predetermined limit. For example, the buffer change rate isadvantageously a buffer fill rate at which the buffer fills and thebuffer change rate is a buffer fill rate. Accordingly, the rate at whichthe buffer fills may be monitored 212. Also, the condition indicative ofcongestion may be determined 222 in response to said buffer fill rateexceeding the first predetermined limit.

In still other embodiments, which are not illustrated in the drawings,it is conceivable to combine the above-mentioned embodiments ofmonitoring 211, 212 a buffer fill level and a rate at which the bufferchanges, respectively.

In response to determining the condition indicative of congestion (YESin FIG. 2A), a congestion notification message 300 is created, orotherwise generated. As can be seen in FIG. 3A, this congestionnotification message 300 includes at least a combination of: (1) a flowidentifier 310, and (2) back-off information 320. Optionally, thecongestion notification message 300 may also include a data field 330indicating the message type, i.e. a congestion notification message.

The flow identifier 310 may identify at least one flow that contributesto the congestion. The back-off information 320 may indicate a suitableback-off to compensate for the congestion caused by the at least oneflow associated with the corresponding flow identifier 310.

FIG. 3B schematically illustrates a first example implementation of thecongestion notification message 300 shown in FIG. 3A. As can be seen inFIG. 3B, the back-off information 320 may in some embodiments includeone or more of the following parameters: back-off rate 321, back-offtime 322, and ramp-up time 323. Furthermore, the flow identifier 310 mayinclude a Packet Data Conversion Protocol (PDCP) Flow Identification(FID) 311. In the example implementation shown in FIG. 3B, the Typefield defines that this is a PDCP Flow ID notification message. The PDCPFlow-ID field identifies the specific flow using the following flow IDvariant: PDCP Flow ID (PDCP-FID). The back-off rate 321 may compriseinformation about how much a second network node shall back-off. This istypically, but not necessarily, expressed in terms of rate (e.g.,bandwidth) and may e.g. be an explicit rate number or described as apercentage back-off from the instantaneously used bandwidth. Theback-off time 322 may comprise information about how long the back-offshould be performed. This is typically, but not necessarily, expressedin terms of time (e.g., seconds). The ramp-up time 323 may compriseinformation about how fast the ramp-up should be, e.g., the shortestallowed time (e.g., in seconds) to get back to previous used rate(bandwidth). The back-off rate 321, back-off time 322 and ramp-up time323 parameter values may all vary from 0 (zero), which is a specialcase, and up to an (in principle) unlimited value, which is also aspecial case.

FIG. 3C schematically illustrates a second example implementation of thecongestion notification message 300 shown in FIG. 3A. As can be seen inFIG. 3C, the flow identifier may include a PDCP Group FlowIdentification 312.

FIG. 3D schematically illustrates a third example implementation of thecongestion notification message 300 shown in FIG. 3A. As can be seen inFIG. 3D, the flow identifier may include a PDCP Multicast Group FlowIdentification 313.

With continued reference to FIG. 2A, the created congestion notificationmessage 300 is also transmitted 240, i.e. sent, to a second networknode. As will be appreciated, the congestion notification message 300may be sent 240 to a single second network node, e.g. using congestionnotification message 300 as illustrated in FIG. 3B. Alternatively, thecongestion notification message 300 may be sent 240 to a group ofseveral second network nodes, e.g. using congestion notification message300 as illustrated in FIG. 3C. In still other embodiments, it ispossible to send 240 a multicast message, e.g. using congestionnotification message 300 as illustrated in FIG. 3D.

Reference is now made to FIG. 2B, which illustrates optional actions, orsteps, in accordance with some embodiments. As can be seen in FIG. 2B, alist of second network node(s) to which the congestion notificationmessage has been transmitted can be stored 242. For example,identifications (ID:s) of each one of said second network node(s) may bestored in this list. The ID may e.g. be an address of the respectivesecond network node(s). Also, the flow identifiers and back-offinformation of all transmitted congestion notification messages may bestored 244.

Reference is now made to FIG. 2E, which illustrates actions, or steps,of a method for back-pressure control. The buffer state of the buffer ismonitored 250. For example, monitoring 250 the buffer state may includedynamically sampling the buffer such that the sampling rate is adjustedin dependence of the buffer state.

Furthermore, a condition indicative of back-pressure is detected 252 inresponse to a change of the buffer state passing a second predeterminedlimit. The exact level, or value, of this second predetermined limitshould be tested an evaluated in each specific case, e.g. in view ofsystem requirements and/or user demands.

In one embodiment, which is schematically illustrated in FIG. 2F, thebuffer state may be a buffer fill level and the change of the bufferstate may be a change of the buffer fill level. The method may hencecomprise monitoring 250A the buffer fill level and determining 252A thecondition indicative of back-pressure in response to the buffer filllevel descending below the second predetermined limit.

In one embodiment, which is schematically illustrated in FIG. 2G, thebuffer state may be a buffer emptying rate at which the buffer emptiesand the change of the buffer state may be a change of the bufferemptying rate. The method may hence comprise monitoring the bufferemptying rate 250B at which the buffer state empties and determining252B the condition indicative of back-pressure in response to saidbuffer emptying rate exceeding the second predetermined limit.

In still other embodiments, which are not illustrated in the drawings,it is conceivable to combine the above-mentioned embodiments describedin conjunction with FIGS. 2F and 2G, respectively.

In response to determining the condition indicative of back-pressure(YES in FIG. 2E), a back-pressure notification message 400 is created254 or otherwise generated.

As can be seen in FIG. 4A, the back-pressure notification message 400may include a flow identifier 310. Also, the back-pressure notificationmessage 400 may include back-pressure compensation information 420.Optionally, the back-pressure notification message 400 may also includea data field 430 indicating the message type, i.e. a back-pressurenotification message 400.

The flow identifier 310 may identify at least one flow that contributesto identifying a flow that contributes to back-pressure. Theback-pressure compensation information 420 may indicate a suitablecompensation for the back-pressure caused by the at least one flowassociated with said flow identifier 310.

FIG. 4B schematically illustrates a first example implementation of theback-pressure notification message 400 shown in FIG. 4A. As can be seenin FIG. 4B, the back-pressure compensation information 420 may in someembodiments include one or more of the following parameters: back-offrate 421, back-off time 422, and ramp-up time 423. Furthermore, the flowidentifier 310 may include a Packet Data Conversion Protocol (PDCP) FlowIdentification (FID) 311. In the example implementation shown in FIG.4B, the Type field defines that this is a PDCP Flow ID notificationmessage. The PDCP Flow-ID field identifies the specific flow using thefollowing flow ID variant: PDCP Flow ID (PDCP-FID). The back-off rate421 may comprise information about how much a second network node shallback-off. This is typically, but not necessarily, expressed in terms ofrate (e.g., bandwidth) and may e.g. be an explicit rate number ordescribed as a percentage back-off from the instantaneously usedbandwidth. The back-off time 422 may comprise information about how longtime the back-off should be performed. This is typically, but notnecessarily, expressed in terms of time (e.g., seconds). The ramp-uptime 423 may comprises information about how fast the ramp-up should be,e.g., the shortest allowed time (e.g., in seconds) to get back toprevious used rate (bandwidth).

FIG. 4C schematically illustrates a second example implementation of theback-pressure notification message 400 shown in FIG. 4A. As can be seenin FIG. 4C, the flow identifier may include a PDCP Group FlowIdentification 312.

FIG. 4D schematically illustrates a third example implementation of theback-pressure notification message 400 shown in FIG. 4A. As can be seenin FIG. 4D, the flow identifier may include a PDCP Multicast Group FlowIdentification 313.

In some embodiments, the flow identifier 310 may additionally comprisean IP address associated with the first network node.

As will be appreciated, the back-pressure notification message 400 maybe similar to the congestion notification message 300 shown in FIGS.3A-3D. Typically, the difference is in the values of the different datafields 421, 422, and 423 (compared with the corresponding values of thecorresponding data fields 321, 322, 323). While the values of the datafields 321, 322, 323 are used to indicate a suitable back-off tocompensate for a detected condition indicative of congestion, the valuesof the data fields 421, 422, and 423 are used to indicate a suitablecompensation for a detected condition indicative of back-pressure in thetransport network.

With continued reference to FIG. 2E, the created back-pressurenotification message 400 is also sent 258, i.e. transmitted, to at leastone second network node. As will be appreciated, the back-pressurenotification message 400 may be sent 240 to a single second networknode, e.g. using congestion notification message 400 as illustrated inFIG. 4B. Alternatively, the back-pressure notification message 400 maybe sent 240 to a group of several second network nodes, e.g. usingcongestion notification message 400 as illustrated in FIG. 4C. In stillother embodiments, it is possible to send 240 a multicast message, e.g.using back-pressure notification message 400 as illustrated in FIG. 4D.

In some embodiments, the method may optionally include transmitting 258the back-pressure notification message to at least one second networknode if and only if a congestion notification message 300 has beenpreviously transmitted to the same at least one second network node.

To this end, the method may comprise checking 256 the stored list ofsecond network nodes as well as the stored flow identifiers and theback-off information of all transmitted congestion notification messagesto identify a second network node(s) that is/are currently compensatingfor congestion. Once identified, the back-pressure notification message400 may be transmitted to each one of the second network node(s) thathas/have been identified to be currently compensating for congestion.

With reference to FIGS. 5A and 5B, it should be understood that the PDCPFID:s described hereinabove (e.g., PDCP-FID, PDCP-GRP-FID,PDCP-MCGRP-FID) may in some embodiments be carried by differentprotocols and in different ways. FIG. 5A shows an example in InternetProtocol version 6, IPv6. FIG. 5B shows an example in Internet Protocolversion 4, IPv4.

Reference is now made to FIG. 6, which schematically illustrates aflowchart of a corresponding method performed by a second network node.This second network node is advantageously a network node that isconfigured for a fifth or subsequent generation telecommunicationnetwork.

As can be seen in FIG. 6, a back-pressure notification message 400 isreceived 610 from a first network node. As can be seen in FIGS. 4A-4D,the back-pressure notification message 400 includes a combination of aflow identifier 310 identifying a flow that contributes to back-pressureand back-pressure compensation information 420 indicating a suitablecompensation for the back-pressure caused by the flow associated withsaid flow identifier 310: Furthermore, one or more parameters areadjusted 520, or otherwise changed, on the basis of said back-pressurecompensation information 420.

The various embodiments described herein may be applied in differentways. For example, the flow control may be provided at IP level,managing IP flow control for PDCP over the midhaul of a 5G RAN. The flowcontrol described in this disclosure may be seen as comprising threemain parts, or functions:

-   -   1. Detection point (i.e. the first network node): the point        where a reduced congestion state is detected and notification        messages (i.e., back-pressure notification messages) are sent        from. It should be appreciated that any intermediate IP router        may also be a detection point.    -   2. Reaction point (i.e. the second network node(s)): the points        where the action is taken on the reduced congestion based on        received notification message. It should be appreciated that any        intermediate IP router may also be a detection point.    -   3. Back-pressure notification messages: The message sent between        detection point and the reaction point, informing the reaction        points of back-pressure and including back-pressure compensation        information to assist reaction points in compensating for a        detected back-pressure.

In some embodiments and for traffic in the PDCP domain, the PDCP flow(s)may be marked with PDCP Flow ID (PDCP-FID, single PDCP flow) and/or(PDCP-GRP-FID, for PDCP group flows), which may for instance be encodedinto the IP flow ID header (IPv6), or in a separate IP option, or anykind of protocol header.

For example, the detection point may identify a congestion state or achange rate of the congestion state by monitoring the buffer. When abuffer decreases to certain buffer level or the buffer emptying ratereaches a certain emptying rate level the notification message may besent to the reaction point(s) being under back-off. In some embodimentsand in order to send the notification message the detection point will,the detection point may use the source IP-address and PDCP-FID and/orPDCP-GRP-FID of the identified flow(s) being under back-off. In case ofsending the message to multiple reaction points at the same time,multicast may be used as an alternative. In the latter case, a specialMulticast PDCP group notification FID (PDCP-MCGRP-FID) may be used. Thiscan be used in both down and uplink direction. As described earlier, thenotification message 400 may include information of changed time toback-off and/or level of back off and/or ramp-up time.

In some embodiments, it is possible to use or otherwise utilize“watermarks”. The working principle of a detection point may then be asfollows. The buffer-level and change-rate of buffer level in eachQuality-of-Service (QoS) queue is checked together with the relatedSource IP-address including PDCP-FID and/or PDCP-GRP-FID.

According to some aspects of the international patent applicationPCT/SE2016/050144 the sampling of the buffer is dynamic, meaning thatwhen there is high buffer occupation the sampling rate is increased andwhen the buffer occupation is low the sampling rate is lower. When thewatermark is passed, the detection point may send a congestionnotification message to the reaction point identified by IP-address andrelated PDCP-FID and/or PDCP-GRP-FID. When multicast is used thedetection point may send to the multicast source specific IP group andmay use the related PDCP-MCGRP-FID. As described earlier, the congestionnotification message 300 may for example comprise information on i) howmuch (expressed as rate) the reaction point(s) should back off, ii) forhow long time (expressed in time) the reaction point(s) should back offand iii) the ramp-up time after a back-off. For further details withrespect to the congestion notification messages, see FIGS. 3A-3D.

A dynamical sampling makes it possible to adaptively adjust, orotherwise change, the sampling rate. For example, when the trafficintensity is low and thus a buffer fill level is low, the sampling ratemay also be adjusted to be low as there is typically no (or, little)need for detailed flow information. Furthermore, when the trafficintensity is low it may be advantageous to reduce the sampling rate asthis will also limit the usage of processing resources and power.However, when the traffic intensity increases the sampling rate may alsobe adjusted to increase, e.g., to make it easier to identify the flow(s)that is/are consuming most bandwidth.

In this disclosure, embodiments are provided to improve the networkusage efficiency even further. For example, an idea is to address thenetwork usage efficiency in a detection point that e.g. monitors whenthe buffer level goes below certain level or when the buffer emptyingrate increases to a certain rate. The detection point may have adatabase storing a list of all reaction points that are under back-offand their respective timer status. Upon detection of a conditionindicative of back-pressure, new notification messages (i.e., theback-pressure notification messages) may be sent to the reactionpoint(s) being under back-off (i.e., the reaction point(s) to which thedetection point has sent congestion notification messages and thathas/have time left on their respective back-off timer). Theback-pressure notification messages may include information related toback-off rate and/or back-off time and/or ramp-up time such that thereaction point(s) may end the back-off and start sending messages (andthus add traffic) again. The detection point may send the back-pressurenotification messages to the reaction point(s) by addressing them withtheir respective IP-address and related PDCP-FID and/or PDCP-GRP-FID.When multicast is used the detection point may send to a multicastsource specific IP group and may use the related PDCP-MCGRP-FID.

Reference is now made to FIG. 7, which illustrates an example embodimentof a first network node 10. The first network node is configured toperform, or otherwise carry out, any of the methods described withreference to FIGS. 2A-2E. The first network node 10 is advantageously anetwork node configured for a 5G or subsequent generationtelecommunications network.

The first network node 10 comprises means 11 adapted to monitor a bufferstate of a buffer. Furthermore, means 12 adapted to determine acondition indicative of back-pressure are provided. The means 12 areadapted to determine the condition indicative of back-pressure inresponse to a change of the buffer state passing a second predeterminedlimit. Still further, the first network node 10 comprises means 13adapted to create a back-pressure notification message 400 in responseto determining the condition indicative of back-pressure. Theback-pressure notification message 400 includes a combination of a flowidentifier 310 and back-pressure compensation information 420. The flowidentifier 310 may identify or otherwise indicate at least one flow thatcontributes to back-pressure. The back-pressure compensation information420 may indicate a suitable compensation for the back-pressure.

The above-mentioned back-pressure compensation information 420typically, but not necessarily, includes one or more of the followingparameters: back-off rate 421, back-off time 422, ramp-up time 423.

In some embodiments, the flow identifier 310 may include a PDCP FID.Alternatively, the flow identifier 310 may include a PDCP Group FID.Alternatively, the flow identifier 310 may include a PDCP MulticastGroup FID. Additionally, the flow identifier 310 may also comprise an IPaddress associated with the first network node.

Moreover, the first network node 10 comprises means 14 adapted totransmit the back-pressure notification message to at least one secondnetwork node.

In some embodiments, means 11 are adapted to dynamically sample thebuffer such that the sampling rate is adjusted in dependence of thebuffer state.

In some embodiments, the buffer state may be a buffer fill level and thechange of the buffer state may be a change of the buffer fill level.Hence, the first network node 10 may comprise means 11 adapted tomonitor the buffer fill level and means 12 adapted to determine thecondition indicative of back-pressure in response to the buffer filllevel descending below the second predetermined limit.

In some embodiments, the buffer state may be a buffer emptying rate atwhich the buffer empties and the change of the buffer state may be achange of the buffer emptying rate. Hence, the first network node 10 maycomprise means 11 adapted to monitor the buffer emptying rate at whichthe buffer state empties and means 12 adapted to determine the conditionindicative of back-pressure in response to said buffer emptying rateexceeding the second predetermined limit.

In advantageous embodiments, the first network node 10 may optionallyalso comprise means 15 adapted to determine a condition indicative ofcongestion in response to a change of the buffer state exceeding a firstpredetermined limit. The means 13 may also be adapted to create acongestion notification message in response to determining the conditionindicative of congestion. The congestion notification message may, e.g.,include a combination of (1) a flow identifier identifying a flow thatcontributes to congestion and (2) back-off information indicating asuitable back-off to compensate for the congestion caused by the flowassociated with said flow identifier. Furthermore, the means 14 may beadapted to transmit the congestion notification message to the at leastone second network node.

In some embodiments, the means 14 adapted to transmit the back-pressurenotification message to the network node is further adapted to transmitthe back-pressure notification message to the second network node onlyin response to that the congestion notification message having beenpreviously transmitted to the same second network node.

With continued reference to FIG. 7, the first network node 10 may alsocomprise means 16 adapted to store a list of second network nodes towhich the congestion notification message has been transmitted and means16 adapted to store the flow identifiers and the back-off information ofall transmitted congestion notification messages. The first network node10 may optionally also comprise means 17 adapted to check the storedlist of second network nodes as well as the stored flow identifiers andthe back-off information of all transmitted congestion notificationmessages to identify a second network node that is currentlycompensating for congestion. For example, the means 14 may be adapted totransmit the back-pressure notification message 400 to each one of theat least one second network node that have been identified to becurrently compensating for congestion, in response to identifying atleast one second node that is currently compensating for congestion.

FIG. 8 illustrates an example implementation of the first network node10 illustrated in FIG. 7. In this example implementation, the firstnetwork node 10 comprises a processor 21 and a memory 22. Also, acommunications interface 23 may be provided in order to allow the firstnetwork node to communicate with other apparatuses (e.g., one or severalsecond network nodes), etc. To this end, the communications interface 23may comprise a transmitter (Tx) and a receiver (Rx). Alternatively, thecommunications interface 23 may comprise a transceiver (Tx/Rx) combiningboth transmission and reception capabilities. The communicationsinterface 23 may include a RF interface allowing the first network nodeto communicate with apparatuses etc. through a radio frequency bandthrough the use of different radio frequency technologies e.g.standardized by the 3rd Generation Partnership Project (3GPP), or anyother wireless technology such as Wi-Fi, Bluetooth®, etcetera.

The memory 22 comprises instructions executable by the processor 21whereby the first network node 10 is operative to:

monitor a buffer state of a buffer;

determine a condition indicative of back-pressure in response to achange of the buffer state passing a second predetermined limit;

create a back-pressure notification message in response to determiningthe condition indicative of back-pressure, the back-pressurenotification message including a combination of (1) a flow identifieridentifying a flow that contributes to back-pressure and (2)back-pressure compensation information indicating a suitablecompensation for the back-pressure caused by the flow associated withsaid flow identifier; and

transmit, by means of the transmitter 23, the back-pressure notificationmessage to a second network node.

In some embodiments, the memory 22 may further comprise instructionsexecutable by the processor 21 whereby the first network node 10 isoperative to dynamically sampling the buffer such that the sampling rateis adjusted in dependence of the buffer state.

In some embodiments, the buffer state may be a buffer fill level and thechange of the buffer state may be a change of the buffer fill level. Thememory 22 may further comprise instructions executable by the processor21 whereby the first network node 10 is operative to monitor the bufferfill level and determine the condition indicative of back-pressure inresponse to the buffer fill level descending below the secondpredetermined limit.

In some embodiments, the buffer state may be a buffer emptying rate atwhich the buffer empties and the change of the buffer state may be achange of the buffer emptying rate. The memory 22 may further compriseinstructions executable by the processor 21 whereby the first networknode 10 is operative to monitor the buffer emptying rate at which thebuffer state empties and determine the condition indicative ofback-pressure in response to said buffer emptying rate exceeding thesecond predetermined limit.

The memory 22 may further comprise instructions executable by theprocessor 21 whereby the first network node 10 is operative to, prior todetermining the condition indicative of back-pressure:

determine a condition indicative of congestion in response to a changeof the buffer state exceeding a first predetermined limit;

create a congestion notification message in response to determining thecondition indicative of congestion, the condition indicative ofcongestion including a combination of (1) a flow identifier identifyinga flow that contributes to congestion and (2) back-off informationindicating a suitable back-off to compensate for the congestion causedby the flow associated with said flow identifier; and

transmit, by means of the transmitter 23, the congestion notificationmessage to the second network node.

The memory 22 may further comprise instructions executable by theprocessor 21 whereby the first network node 10 is operative to transmit(by means of the transmitter 23) the back-pressure notification messageto the second network node only in response to that the congestionnotification message has been previously transmitted to the same secondnetwork node.

A memory 24 may be used or otherwise utilized to tore a list of secondnetwork nodes to which the congestion notification message has beentransmitted. The memory 24 may also store the flow identifiers and theback-off information of all transmitted congestion notificationmessages;

The memory 22 may further comprise instructions executable by theprocessor 21 whereby the first network node 10 is operative to checkingthe stored list of second network nodes as well as the stored flowidentifiers and the back-off information of all transmitted congestionnotification messages to identify a second network node that iscurrently compensating for congestion. Furthermore, the memory 22 mayfurther comprise instructions executable by the processor 21 whereby thefirst network node 10 is operative to transmit the back-pressurenotification message, by means of the transmitter 23, to each one of theat least one second network node that has been identified to becurrently compensating for congestion. This may be performed in responsethat at least one second node that is currently compensating forcongestion have been identified.

Reference is now made to FIG. 9, which illustrates another exampleimplementation of the first network node 10. In this exampleimplementation, the first network node 10 comprises a processor 31, andone or several modules 32 a-h. Also, a communications interface may beprovided in order to allow the first network node 10 to communicate withother apparatuses (e.g., one or several second network nodes), etc. Tothis end, the communications interface may comprise a transmitter (Tx)and/or a receiver (Rx). Alternatively, the communications interface maycomprise a transceiver (Tx/Rx) combining both transmission and receptioncapabilities. The communications interface may include a RF interfaceallowing the first network node 10 to communicate with apparatuses etc.through a radio frequency band through the use of different radiofrequency technologies e.g. standardized by the 3rd GenerationPartnership Project (3GPP), or any other wireless technology such asWi-Fi, Bluetooth®, etcetera.

A buffer state monitoring module 32 a is configured to monitoring abuffer state of a buffer. Furthermore, a back-pressure detection module32 b is provided for determining a condition indicative of back-pressurein response to a change of the buffer state passing a secondpredetermined limit. Still further, a back-pressure notification messagegeneration module 32 c is configured to create a back-pressurenotification message in response to determining the condition indicativeof back-pressure. The back-pressure notification message includes acombination of a flow identifier identifying a flow that contributes toback-pressure and back-pressure compensation information indicating asuitable compensation for the back-pressure caused by the flowassociated with said flow identifier. Furthermore, the transmitter (Tx)is configured to transmit the back-pressure notification message to asecond network node.

In some embodiments, the buffer state monitoring module 32 a may beconfigured to dynamically sample the buffer such that the sampling rateis adjusted in dependence of the buffer state.

In some embodiments, the buffer state may be a buffer fill level and thechange of the buffer state may be a change of the buffer fill level. Thebuffer state monitoring module 32 a may be configured to monitor thebuffer fill level and the back-pressure detection module 32 b may beconfigured to determine the condition indicative of back-pressure inresponse to the buffer fill level descending below the secondpredetermined limit.

In some embodiments, the buffer state may be a buffer emptying rate atwhich the buffer empties and the change of the buffer state may be achange of the buffer emptying rate. The buffer state monitoring module32 a may be configured to monitor the buffer emptying rate at which thebuffer state empties; and the back-pressure detection module 32 b may beconfigured to determine the condition indicative of back-pressure inresponse to said buffer emptying rate exceeding the second predeterminedlimit.

The first network node 10 may additionally comprise a congestiondetection module 32 d configured to determine a condition indicative ofcongestion in response to a change of the buffer state exceeding a firstpredetermined limit. Still further, a congestion notification messagegeneration module 32 e is configured to create a congestion notificationmessage in response to determining the condition indicative ofcongestion. The congestion notification message may include acombination of a flow identifier identifying a flow that contributes tocongestion and back-off information indicating a suitable back-off tocompensate for the congestion caused by the flow associated with saidflow identifier. The transmitter (Tx) may further be configured totransmit the congestion notification message to the second network node.

In some embodiments, the transmitter (Tx) is configured to transmit theback-pressure notification message to the second network node only inresponse to that a congestion notification message has been previouslytransmitted to the same second network node.

Optionally, a first storage module 32 f for storing a list of secondnetwork nodes to which the congestion notification message has beentransmitted may also provided. Also, a second storage module 32 g forstoring the flow identifiers and the back-off information of alltransmitted congestion notification messages may be provided. A checkingmodule 32 h may also be provided for checking the stored list of secondnetwork nodes as well as the stored flow identifiers and the back-offinformation of all transmitted congestion notification messages toidentify a second network node that is currently compensating forcongestion. The transmitter (Tx) may, e.g., be configured to transmitthe back-pressure notification message to each one of the at least onesecond network node that has been identified to be currentlycompensating for congestion.

Reference is now made to FIG. 10, which illustrates an exampleembodiment of a second network node 40. The second network node 40 isconfigured to perform, or otherwise carry out, any of the methoddescribed with reference to FIG. 6. The second network node 40 isadvantageously a network node configured for a 5G or a subsequentgeneration telecommunications network.

The second network node 40 is suitable for flow control in a transportnetwork. As can be seen in FIG. 10, the second network node 40 comprisesmeans 31 adapted to receive, from a first network node, a back-pressurenotification message 400. As described earlier, the back-pressurenotification message 400 includes a combination of: (1) a flowidentifier 310 identifying a flow that contributes to back-pressure and(2) back-pressure compensation information 420 indicating a suitablecompensation for the back-pressure caused by the flow associated withsaid flow identifier 310. Furthermore, the second network node 30comprises means 32 adapted to adjust one or more parameters on the basisof said back-pressure compensation information.

FIG. 11 illustrates an example implementation of the second network node40 illustrated in FIG. 10. In this example implementation, the secondnetwork node 40 comprises a processor 43 and a memory 44. Also, acommunications interface 45 may be provided in order to allow the firstnetwork node to communicate with other apparatuses (e.g., a firstnetwork node), etc. To this end, the communications interface 45 maycomprise a transmitter (Tx) and a receiver (Rx). Alternatively, thecommunications interface 45 may comprise a transceiver (Tx/Rx) combiningboth transmission and reception capabilities. The communicationsinterface 45 may include a RF interface allowing the first network nodeto communicate with apparatuses etc. through a radio frequency bandthrough the use of different radio frequency technologies e.g.standardized by the 3rd Generation Partnership Project (3GPP), or anyother wireless technology such as Wi-Fi, Bluetooth®, etcetera.

The memory 44 comprises instructions executable by the processor 43whereby the second network node 40 is operative to receive (from a firstnetwork node) a back-pressure notification message by means of thereceiver 45. As described earlier, the back-pressure notificationmessage 400 includes a combination of: (1) a flow identifier 310identifying a flow that contributes to back-pressure and (2)back-pressure compensation information 420 indicating a suitablecompensation for the back-pressure caused by the flow associated withsaid flow identifier 310. Furthermore, the memory 44 comprisesinstructions executable by the processor 43 whereby the second networknode 40 is operative to adjust one or more parameters on the basis ofsaid back-pressure compensation information.

Reference is now made to FIG. 12, which illustrates another exampleimplementation of the second network node 40. In this exampleimplementation, the second network node 40 comprises a processor 46, andone or several modules 47 a. Also, a communications interface may beprovided in order to allow the second network node 40 to communicatewith other apparatuses (e.g., a first network node), etc. To this end,the communications interface may comprise a transmitter (Tx) and/or areceiver (Rx). Alternatively, the communications interface may comprisea transceiver (Tx/Rx) combining both transmission and receptioncapabilities. The communications interface may include a RF interfaceallowing the second network node 40 to communicate with apparatuses etc.through a radio frequency band through the use of different radiofrequency technologies e.g. standardized by the 3rd GenerationPartnership Project (3GPP), or any other wireless technology such asWi-Fi, Bluetooth®, etcetera.

The receiver (Rx) is configured to receive the back-pressurenotification message, wherein the back-pressure notification message 400includes said combination of (1) a flow identifier 310 identifying aflow that contributes to back-pressure and (2) back-pressurecompensation information 420 indicating a suitable compensation for theback-pressure caused by the flow associated with said flow identifier310. Also, a parameter adjustment module 47 a is configured to adjust orotherwise change one or more parameters on the basis of said back-offinformation.

FIG. 13 shows an example of a computer-readable medium, in this examplein the form of a data disc 1300. In one embodiment the data disc 1300 isa magnetic data storage disc. The data disc 1300 is configured to carryinstructions 1310 that can be loaded into a memory of an apparatus. Uponexecution of said instructions by a processor of the apparatus, theapparatus is caused to execute a method or procedure according to anyone of the methods described in this disclosure. The data disc 1300 isarranged to be connected to or within and read by a reading device (notshown), for loading the instructions into the processor. One suchexample of a reading device in combination with one (or several) datadisc(s) 1300 is a hard drive. It should be noted that thecomputer-readable medium can also be other mediums such as compactdiscs, digital video discs, flash memories or other memory technologiescommonly used. In such an embodiment the data disc 1300 is one type of atangible computer-readable medium. The instructions may alternatively bedownloaded to a computer data reading device, such as a computer orother apparatus capable of reading computer coded data on acomputer-readable medium, by comprising the instructions in acomputer-readable signal (not shown) which is transmitted via a wireless(or wired) interface (for example via the Internet) to the computer datareading device for loading the instructions into a processor of theapparatus. In such an embodiment, the computer-readable signal is onetype of a non-tangible computer-readable medium.

The various embodiments described herein suggest monitoring a bufferstate of a buffer, e.g., by dynamically sampling the buffer such thatthe sampling rate is adjusted in dependence of the buffer state. Upon adetermination by a first network node (a.k.a. detection point) of acondition indicative of back-pressure in response to a change of thebuffer state passing a predetermined limit, a back-pressure notificationmessage can be created or otherwise generated. This back-pressurenotification message can be transmitted from the first network node toone or several second network nodes (a.k.a. reaction points). Based onthe received back-pressure notification message, the one or severalsecond network nodes may compensate for a detected back-pressure byadjusting one or more of its parameters based on received informationback-pressure compensation information including e.g. suggested back-offtime, suggested back-off rate, and/or suggested ramp-up time. Hence, asecond network node may adjust i) the time during which it performsback-off, ii) the rate at which back-off is performed, and/or iii) theramp-up time for the back-off. Upon adjusting one or more of itsparameters, it is possible for the second network node to adaptivelyadjust its behavior in dependence of a condition indicative ofback-pressure detected by any first network node in the network, e.g.following an earlier detection of a condition indicative of congestionmade by the same first network node. This way it is possible toadaptively influence the PDCP transmissions/retransmissions in thenetwork at appropriate times. As a result, the transport network mayoperate more efficiently. Also, the user experience may thus beimproved.

In the detailed description hereinabove, for purposes of explanation andnot limitation, specific details are set forth in order to provide athorough understanding of various embodiments described in thisdisclosure. In some instances, detailed descriptions of well-knowndevices, components, circuits, and methods have been omitted so as notto obscure the description of the embodiments disclosed herein withunnecessary detail. All statements herein reciting principles, aspects,and embodiments disclosed herein, as well as specific examples thereof,are intended to encompass both structural and functional equivalentsthereof. Additionally, it is intended that such equivalents include bothcurrently known equivalents as well as equivalents developed in thefuture, i.e., any elements developed that perform the same function,regardless of structure. Thus, for example, it will be appreciated thatblock diagrams herein can represent conceptual views of illustrativecircuitry or other functional units embodying the principles of thedescribed embodiments. Similarly, it will be appreciated that any flowcharts and the like represent various processes which may besubstantially represented in computer readable medium and so executed bya computer or processor, whether or not such computer or processor isexplicitly shown. The functions of the various elements includingfunctional blocks, may be provided through the use of hardware such ascircuit hardware and/or hardware capable of executing software in theform of coded instructions stored on the above-mentioned computerreadable medium. Thus, such functions and illustrated functional blocksare to be understood as being either hardware-implemented and/orcomputer-implemented, and thus machine-implemented. In terms of hardwareimplementation, the functional blocks may include or encompass, withoutlimitation, digital signal processor (DSP) hardware, reduced instructionset processor, hardware (e.g., digital or analog) circuitry includingbut not limited to application specific integrated circuit(s) (ASIC(s)),and/or field programmable gate array(s) (FPGA(s)), and (whereappropriate) state machines capable of performing such functions. Interms of computer implementation, a computer is generally understood tocomprise one or more processors or one or more controllers. Whenprovided by a computer or processor or controller, the functions may beprovided by a single dedicated computer or processor or controller, by asingle shared computer or processor or controller, or by a plurality ofindividual computers or processors or controllers, some of which may beshared or distributed. Moreover, use of the term “processor” or“controller” may also be construed to refer to other hardware capable ofperforming such functions and/or executing software, such as the examplehardware recited above.

Modifications and other variants of the described embodiments will cometo mind to one skilled in the art having benefit of the teachingspresented in the foregoing description and associated drawings.Therefore, it is to be understood that the embodiments are not limitedto the specific example embodiments described in this disclosure andthat modifications and other variants are intended to be included withinthe scope of this disclosure. As a mere example, it should beappreciated that it is conceivable to use or otherwise utilize several(i.e., two or more) second predetermined limits. This way it may forinstance be possible to determine different levels of back-pressure,e.g. from low back-pressure to high back-pressure. Also, theback-pressure compensation information indicating a suitablecompensation for the back-pressure may be tailored to compensate forsaid different levels of back-pressure. Likewise, it should beappreciated that it is conceivable to use or otherwise utilize severalfirst predetermined limits. This way it may for instance be possible todetermine different levels of congestion, e.g. from low congestion tohigh congestion. Also, the back-off information indicating the suitableback-off to compensate for the congestion may be tailored to compensatefor said different levels of congestion.

Furthermore, although specific terms may be employed herein, they areused in a generic and descriptive sense only and not for purposes oflimitation. Therefore, a person skilled in the art would recognizenumerous variations to the described embodiments that would still fallwithin the scope of the appended claims. As used herein, the terms“comprise/comprises” or “include/includes” do not exclude the presenceof other elements or steps. Furthermore, although individual featuresmay be included in different embodiments, these may possiblyadvantageously be combined, and the inclusion of different numberedembodiments does not imply that a combination of features is notfeasible and/or advantageous. In addition, singular references do notexclude a plurality.

What is claimed is:
 1. A method of back-pressure control in a transportnetwork, the method being performed by a second network node, the methodcomprising: receiving a congestion notification message from a firstnetwork node, in which the first network node generated the congestionnotification message when the first network node determined a conditionindicative of congestion, in response to a change of a buffer state of abuffer exceeding a first predetermined limit; receiving a back-pressurenotification message from the first network node subsequent to thecongestion notification message, in which the first network nodegenerated the back-pressure notification message when the first networknode determined a condition indicative of back-pressure, in response toa change of the buffer state of the buffer passing a secondpredetermined limit, the back-pressure notification message includingback-pressure compensation information; and adjusting, at the secondnetwork node, one or more parameters on a basis of the back-pressurecompensation information.
 2. The method of claim 1, wherein theback-pressure notification message further including a flow identifiercomprising a Packet Data Convergence Protocol (PDCP) Flow Identification(FID), a PDCP Group FID, or a PDCP Multicast Group FID.
 3. The method ofclaim 1, wherein the back-pressure notification message furtherincluding a flow identifier identifying a flow that contributes to theback-pressure.
 4. The method of claim 3, wherein the back-pressurecompensation information indicating a suitable compensation for theback-pressure caused by the flow associated with the flow identifier. 5.The method of claim 3, wherein the back-pressure compensationinformation including a back-off rate to indicate an amount of back-offadjustment.
 6. The method of claim 3, wherein the back-pressurecompensation information including a back-off time to indicate a timeduration of back-off adjustment.
 7. The method of claim 3, wherein theback-pressure compensation information including a ramp-up time toindicate a time rate in returning from a back-off condition to aprevious state of the second network node.
 8. A second network node forback-pressure control in a transport network, the second network nodecomprising: a processor; and a memory containing instructions which,when executed by the processor, cause the second network node to performoperations to: receive a congestion notification message from a firstnetwork node, in which the first network node generated the congestionnotification message when the first network node determined a conditionindicative of congestion, in response to a change of a buffer state of abuffer exceeding a first predetermined limit; receive a back-pressurenotification message from the first network node subsequent to thecongestion notification message, in which the first network nodegenerated the back-pressure notification message when the first networknode determined a condition indicative of back-pressure, in response toa change of the buffer state of the buffer passing a secondpredetermined limit, the back-pressure notification message includingback-pressure compensation information; and adjust one or moreparameters on a basis of the back-pressure compensation information. 9.The second network node of claim 8, wherein the back-pressurenotification message further including a flow identifier comprising aPacket Data Convergence Protocol (PDCP) Flow Identification (FID), aPDCP Group FID, or a PDCP Multicast Group FID.
 10. The second networknode of claim 8, wherein the back-pressure notification message furtherincluding a flow identifier identifying a flow that contributes to theback-pressure.
 11. The second network node of claim 10, wherein theback-pressure compensation information indicating a suitablecompensation for the back-pressure caused by the flow associated withthe flow identifier.
 12. The second network node of claim 10, whereinthe back-pressure compensation information including a back-off rate toindicate an amount of back-off adjustment.
 13. The second network nodeof claim 10, wherein the back-pressure compensation informationincluding a back-off time to indicate a time duration of back-offadjustment.
 14. The second network node of claim 10, wherein theback-pressure compensation information including a ramp-up time toindicate a time rate in returning from a back-off condition to aprevious state of the second network node.
 15. A non-transitorycomputer-readable storage medium containing instructions which, whenexecuted on at least one processor, are capable of causing a secondnetwork node to perform operations for back-pressure control in atransport network comprising: receiving a congestion notificationmessage from a first network node, in which the first network nodegenerated the congestion notification message when the first networknode determined a condition indicative of congestion, in response to achange of a buffer state of a buffer exceeding a first predeterminedlimit; receiving a back-pressure notification message from the firstnetwork node subsequent to the congestion notification message, in whichthe first network node generated the back-pressure notification messagewhen the first network node determined a condition indicative ofback-pressure, in response to a change of the buffer state of the bufferpassing a second predetermined limit, the back-pressure notificationmessage including back-pressure compensation information; and adjusting,at the second network node, one or more parameters on a basis of theback-pressure compensation information.
 16. The non-transitorycomputer-readable storage medium of claim 15, wherein the instructionsare capable of operating on the back-pressure notification message thatincludes a flow identifier identifying a flow that contributes to theback-pressure.
 17. The non-transitory computer-readable storage mediumof claim 16, wherein the instructions are capable of operating on theback-pressure compensation information indicating a suitablecompensation for the back-pressure caused by the flow associated withthe flow identifier.
 18. The non-transitory computer-readable storagemedium of claim 16, wherein the instructions are capable of operating onthe back-pressure compensation information that includes a back-off rateto indicate an amount of back-off adjustment.
 19. The non-transitorycomputer-readable storage medium of claim 16, wherein the instructionsare capable of operating on the back-pressure compensation informationthat includes a back-off time to indicate a time duration of back-offadjustment.
 20. The non-transitory computer-readable storage medium ofclaim 16, wherein the instructions are capable of operating on theback-pressure compensation information that includes a ramp-up time toindicate a time rate in returning from a back-off condition to aprevious state of the second network node.